import turtle
import random
arr = ['red','green','pink','gold','blue','yellow','black','orange']
n = len(arr)
turtle.title('是同心圆呢~')
t = turtle.Turtle()

t.speed(10)

for radius in range(20,101,20):
    t.penup()
    t.goto(0,-radius) #移动到新圆的起点
    t.pendown()
    t.color(arr[random.randint(0,n-1)])
    t.circle(radius)

turtle.done()